This invention relates to a method and apparatus for controlling tapping with a tapper or the like.
When tapping is performed with a tapper, it is necessary to control the rotationship of a spindle and the feed on a feed shaft in a manner to maintain a certain correlation between the relative rotational angles and the relative feeds of a work and a tapper or, more particularly, the phase difference between the work and the tapper must constantly be equal to zero. In the prior art, therefore, tapping has been controlled by providing a positional control function on the control of the spindle similarly to that of the feed shaft to thereby synchronize rotation of the spindle and feed on the feed shaft.
FIG. 1 is a block diagram showing an embodiment of a tapping control device to realize the above mentioned prior art control method. In this device, when a command for the relative rotation angle (referred to as "rotation angle of the spindle" hereinafter) of the spindle and a command for the relative feed (referred to as "feed on the feed shaft" hereinafter) on the feed shaft are inputted to a normal synchronization controlling section 2 from a rotation angle/feed command section 1, a control command for synchronizing rotation of the spindle and feed of the feed shaft is respectively sent to a spindle rotation controlling section 3 and a feed shaft feeding controlling section 6. The drive of a spindle driving section 4 is controlled in accordance with the rotation angle of the spindle which is detected by a spindle rotation angle detecting section 5, and the drive of a feed shaft driving section 7 by the feed on the feed shaft which is detected by a feed shaft feeding detecting section 8.
In the above mentioned prior art controller for tapping, when tapping is suspended, for instance, due to a failure in the tapper while the controller is being operated, the subsequent operation cannot be re-started automatically. The operator, instead, has to turn and remove the tapper manually with utmost care for resetting the process in order to minimize the damage to the machined portion.